1. Field of the Invention
The present invention relates to a retention mechanism for securing an upright CPU module to a socket connector mounted on a printed circuit board (PCB), and particularly to a retention mechanism having an improved hold-down structure for securing the retention mechanism to the PCB.
2. Description of the Prior Art
A retention mechanism has been developed to retain an upright CPU module in a slot connector mounted on a mother board, as is disclosed in prior art Taiwan patent application Nos. 86211054 and 86207803 and U.S. Pat. No. 6,031,725.
Referring to FIG. 6, a prior art retention mechanism 4 comprises a retention housing 40, at least one board lock post 60 and at least one pin 50 fitting in the post 60. The housing 40 has a rear wall 41 and a pair of bottom plates 42 extending forward from the rear wall 41. A slot 43 is defined in a middle, lower portion of the housing 40 and between a pair of side walls 45 for fittingly receiving one end of a slot connector (not shown) mounted on a PCB (not shown). The board lock post 60 comprises a cylindric head 61 and an insertion leg 63 to be inserted through a hole 44 defined in the bottom plate 42 and retained in the PCB. A hole 62 is defined in the post 60. When the pin 50 is inserted into the hole 62, it expands the insertion leg 63 to complete a secure connection between the retention mechanism 4 and the PCB. A passage 46 is formed between a pair of heat sink fixing brackets 48 and is located above and communicating with the slot 43. A lateral edge of the CPU module is inserted through the passage 46 to a position where the module is electrically connected with the slot connector.
However, there is no structure which can effectively hold the pin 50 in position in the hole 62. Thus, the pin 50 may spring out of the post 60 because of vibration during transportation and use, which will result in the retention mechanism 40 not effectively retaining the CPU module to the slot connector, thereby adversely affecting the electrical connection therebetween.
Hence, an improved retention mechanism is required to overcome the disadvantages of the prior art.
A main object of the present invention is to provide a retention mechanism which is provided with a hold-down structure for securing the mechanism to a PCB.
To fulfil the above mentioned object, a retention mechanism of the present invention comprises a retention housing, a pair of board lock posts extending through a bottom plate of the housing and retained in the PCB and a pair of pins. The retention housing defines a slot for effectively accommodating one end of an electrical connector therein and comprises a rear wall from which at least a stopper projects. Each pin comprises a head portion and a pin body inserted in a corresponding board lock post. The head portion is formed by symmetrically cutting out two arc portions from a dummy cylinder and comprises a pair of planar side surfaces and a pair of arcuate side surfaces. A distance between a longitudinal axis of the pin body and a front face of the stopper is shorter than that between the axis and an arcuate side surface, while it is longer than that between the axis and the planar side surface. The pin is rotatably turned a proper angle in a corresponding board lock post so that the head portion thereof is depressed by a corresponding stopper, which keeps the pin from springing out of the post during transportation and use.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of the present embodiment when taken in conjunction with the accompanying drawings.